Were both in production or just the R4? If only the R4 was seen for the most part then it might have been the Back Bias generator /P0 change I mentioned earlier. -----Original Message----- From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Gerrit Heitsch Sent: Sunday, August 14, 2011 2:39 PM To: firstname.lastname@example.org Subject: Re: 264 Series and their chips On 08/14/2011 08:20 PM, Bil Herd wrote: > Ah, forgot about the speed, we didn't kick that on till later in the > design cycle. > > I would think that the 75/85 versions should work at double clock as > in many ways it's access times are already running at that speed, it > will also depend on supporting chips speeds to some degree too I think , I.E. > 150ns DRAMs would help, etc. I would think that one of the > problematic areas would be getting the address out and through the > MUX/257's in time for /RAS, and the R/W line in time for /WE to be valid for a clean write. If you can still find 41464 RAMs, they are mostly from old VGA cards and those usually use 120ns and faster. So RAM speed shouldn't be a problem. Another way would be to do what I did with a C64, replace the DRAMs with a 128Kx8 SRAM. In the C64 the VIC supplies multiplexed addresses already so I had to demultiplex them with a 74HCT573 first and use _RAS or'ed with _CAS as chip select for the RAM. Since TED doesn't supply multiplexed addresses and _CAS is not routed through the PLA the whole setup should be way easier, possibly needs only _CAS as chip select. Currently I don't have a spare 8500 to try this with though. Do you happen to remember the difference between the 8501R1 and the 8501R4? I couldn't find any information concerning what was changed between R1 and R4. Gerrit > > Bil > > -----Original Message----- > From: email@example.com > [mailto:firstname.lastname@example.org] On Behalf Of Gerrit Heitsch > Sent: Sunday, August 14, 2011 1:45 PM > To: email@example.com > Subject: Re: 264 Series and their chips > > On 08/14/2011 07:17 PM, Bil Herd wrote: >> We made the original 7501/8501 with a 6510 and a 74ls74 on a small >> tower, there wasn't a dependency on the excat mapping of the I/O >> p[ort at the time, but should be something you can put together. > > Even if the difference between I/O-Ports (6510 = P0-P5 and 7501 = > P0-P4,P6-P7) can be worked around (patching all KERNAL locations and > ignoring tape functions), the question is, will the 6510 or the 8500 > work with 1.77 MHz the 8501 runs at part or all of the time? I don't > remember ever seeing a 6510A and the 6510T from the 1551 which > supposedly runs on 2MHz seems to be even more rare than a 8501. > > BTW: In a PAL 264 system, you can push the CPU to 2.2MHz by setting > TED to 'display off' and 'NTSC'. You don't get usable video output, > but double speed compared to normal. Never crashed on me, but I always > had heatsinks on TED and CPU back then. > > > >> >> Bil Herd >> >> -----Original Message----- >> From: firstname.lastname@example.org >> [mailto:email@example.com] On Behalf Of >> Ruud@Baltissen.org >> Sent: Saturday, August 13, 2011 12:23 PM >> To: firstname.lastname@example.org >> Subject: Re: 264 Series and their chips >> >> Hallo Gerrit, >> >> >> Have you ever thought about replacing the 8501 with a 8502 from a >> C128? So far I found four differences: >> - the 8501 has this MUX input (or output? I have no idea what it >> does) which the C128 lacks >> - the 8502 has an "extra" NMI input compared to the 8501 >> - the 8501 lacks the P5 I/O pin, the 8502 P7 >> - pinout doesn't match >> If the MUX gate doesn't spoil things, what about using the 8502? >> Regarding P5/P7: you either don't use the cassette recorder anymore >> or adjust the bits of the Kernal. >> >> Just my two cents... >> >> >> -- >> ___ >> / __|__ >> / / |_/ Groetjes, Ruud Baltissen >> \ \__|_\ >> \___| http://Ruud.C64.org >> >> >> >> >> >> >> >> Message was sent through the cbm-hackers mailing list >> >> Message was sent through the cbm-hackers mailing list >> >> > > > Message was sent through the cbm-hackers mailing list > > Message was sent through the cbm-hackers mailing list > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2011-08-14 20:00:18
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